1. Field of the Invention
The invention relates to a lock for the gate which closes the discharge opening of a hopper railway car or truck, which prevents opening of the gate until the lock has been released and which holds the gate in its closed position after the gate has been closed.
2. Description of Prior Art
Gates, or sliding doors, for closing and sealing a discharge opening in a hopper car are well known in the art. See, for example, U.S. Pat. Nos. 2,926,963; 2,962,325; 3,956,996; 4,301,741; 4,360,295; 4,388,026; 4,450,773 and 4,617,868. Generally speaking, the gate closes an opening in the bottom of a car to retain the lading, which usually is particulate in the car until it is desired to discharge the lading from the car. The gate is moved from its closed position to uncover the opening and permit the discharge of the lading.
When the car is empty, the force to move the gate is small relative to the force required when the car is full and the lading contacts the gate. In some cases, the force of gravity is used to assist and maintain the closing of the gate of an empty car. However, a manually operable mechanism is used for opening and closing the gate and various devices are used for locking the mechanism when the gate is closed.
Such manually operable mechanism can, for example, be a rack or racks secured to the gate and having teeth engageable with the teeth of one or more manually rotatable pinion gears mounted on a shaft having an end, which is square in cross-section, for receiving a wrench or tool or which has through holes for receiving a rod or bar, for rotating the shaft and the pinion gear or gears in one direction or another for opening and closing the gate.
Also, it is customary to lock the gate operating mechanism in the position thereof in which the gate is closed to prevent unintentional opening of the gate during travel of the car. Also, a seal, such as a wire sealing band, may be attached to the locking device so that the latter cannot be unlocked without breaking the seal.
A problem with prior art gate operating mechanisms is that workmen often attempt to rotate the rotatable shaft carrying the pinion gear or gears without opening or releasing the lock and cause damage to the lock gate and/or drive system.
Another problem is that resilient seals for sealing the gate to the periphery of the discharge opening develop set and wear so that a lock which operates only in one position of the gate does not, after a period of use, hold the gate in a position which provide a satisfactory seal between the gate and the periphery of the discharge opening.